Pig slaughterhouses classify the individual slaughter animals to pay the pig producer in accordance with the quality of the animals supplied. Classification of slaughter hogs is determined by means of some meat and fat thickness measurements which an operator performs with a gun-lke instrument.
The instrument has a pointed probe which the operator inserts into the carcass at predetermined locations. During the passage into or out of the carcass the measuring means of the probe detect transition from one material to another, e.g. from meat to fat.
The detection may be based on different conductivity of the materials or on changed reflection of light.
The actual penetration depth of the probe in the procedure is determined by a reference plate which is movably positioned on the instrument and which constantly engages the surface of the carcass under the action of a spring. The plate is firmly mounted on the end of one or two slide rods acting on a position meter which is incorporated in the instrument. Thus, the meter provides a signal which represents the actual penetration depth of the probe with respect to the rind surface.
The probe and depth signals are coupled in a control unit to a measurement result for the meat and fat thickness. The results can be related to other parameters, such as weight, in a connected calculating unit so as to automatically provide a value of the so-called meat percentage. This determines the price categroy to be paid for a particular carcass.
The method described requires training of special classifying operators who must be able to operate the instrument correctly.
The measurement results are subject to some uncertainty, which is parly owing to the system and partly to the operator.